Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension and Other Postretirement Benefits
Pension and other postretirement benefit contributions
Contributions to pension and other postretirement benefit plans	$ 98
Expected full year contributions to pension and other postretirement benefit plans during the year	280
Other Postretirement Benefits Plan
Components of net periodic benefit cost:
Service cost	23	$ 20
Interest cost	26	34
Expected return on plan assets	(3)	(5)
Amortization of prior service cost / (credit)	(9)	(10)
Gain on remeasurement of a non-U.S. pension obligation	0	0
Net periodic benefit cost (benefit)	37	39
UNITED STATES
Components of net periodic benefit cost:
Service cost	0	29
Interest cost	121	150
Expected return on plan assets	(198)	(181)
Amortization of prior service cost / (credit)	0	0
Gain on remeasurement of a non-U.S. pension obligation	0	0
Net periodic benefit cost (benefit)	(77)	(2)
Foreign Plan
Components of net periodic benefit cost:
Service cost	14	21
Interest cost	19	23
Expected return on plan assets	(35)	(37)
Amortization of prior service cost / (credit)	0	0
Gain on remeasurement of a non-U.S. pension obligation	(254)	0
Net periodic benefit cost (benefit)	$ (256)	$ 7